Summary of the National Advisory Committee on Immunization (NACI) rapid response: Updated guidance on the use of Imvamune® for the prevention of mpox.

Abstract

Background: The National Advisory Committee on Immunization (NACI) previously released guidance in May of 2024 regarding the use of Imvamune® for the prevention of mpox in the context of a routine immunization program. Since the release of this guidance, the emergence of a novel subclade of mpox (clade Ib) has led to a shifting epidemiological landscape and several international jurisdictions have, therefore, revised their Imvamune guidance.

Objective: To summarize the updated NACI guidance on the use of Imvamune for the prevention of mpox.

Methods: NACI reviewed data on the current epidemiology of mpox, both in Canada and internationally, current evidence on Imvamune vaccination coverage in Canada, and published scientific literature regarding the effectiveness, immunogenicity and safety of Imvamune. NACI has also considered additional factors including ethics, equity, feasibility and acceptability. Guidance on the use of Imvamune in the context of international travel was developed in collaboration with the Canadian Committee to Advise on Tropical Medicine and Travel.

Results: NACI concluded that available evidence supports the limited expansion of groups considered at high risk of mpox.

Conclusion: NACI now recommends that in addition to previously identified groups at high risk of mpox, certain travellers to areas with ongoing community transmission of mpox virus clade I should receive Imvamune. Healthcare workers travelling internationally to support mpox outbreaks should also receive Imvamune, and domestic healthcare workers with a high risk of frequent exposure may consider vaccination with Imvamune on an individual basis.